"The past, the present and the
future, they exist as one, they breathe together."
(Annorax, VOY: "Year of Hell")

VOY: ParallaxVoyager receives a distress call and
unintentionally gets trapped within the event horizon of a
quantum singularity. Every alleged way out leads back to a place
inside the event horizon, or, more precisely, Voyager actually
does not leave this place, even when the ship seems to travel at
warp speed. The second ship is identified as another Voyager,
probably a "temporal reflection" from another
time. Although there is no real time travel, predestination is
implied, since the distress call from Voyager itself was the
incentive to approach the black hole.

However, it is highly
improbable that a quantum singularity or black hole has the shown
effects, no matter if in Star Trek or in the real world. The event horizon is defined as the radius of a black hole inside which any energy or mass is definitely
trapped, but only the basic idea is used in this episode. The
real effect of a black hole would be that for an external
observer time stands still on a starship near the event horizon,
while it becomes invisible as soon as it is inside. Besides, it
is highly questionable if the SIF can balance out the extreme
gravity force or space distortion near or even inside the event
horizon. The above described hallucination effect that the ship
seems to leave the event horizon is really odd and deserves no
further consideration. After all, it is acceptable that Voyager
can leave the event horizon by means of Treknology (dekyon
particles in this case).Classification: parallel time levels, with predestination phenomenon

VOY: Time and AgainVoyager arrives at a planet, the surface of
which has been completely devastated by an explosion, and no life
exists any more. Down on the planet, Capt. Janeway and Lt. Paris
disappear through a subspace rift and arrive at a time prior to
the explosion when the population is still alive. They learn
about power plants employing polaric energy, which is connected
with deadly risks. They join a group of people who plan to
intrude into the power plant in order to protest against it. The
planet is truly Earth-like. Not only do the inhabitants look
exactly like humans, they also employ Arabic figures, and the
anti-polaric demonstration is familiar too.

The surprising outcome is that not the manipulation
of the power plant is the cause for the explosion, but the
attempt to save Janeway and Tom through a subspace tunnel, which
destabilizes the polaric power source. So actually the Voyager
crew is unintentionally responsible for the disaster. This
episode seems to be based on a predestined timeline, since the
effect of the time travel is evident before the time travel
occurs. However, if the timeline were really predestined, all
events would be unchangeable, and neither the planet nor the two
officers could be saved. Voyager would have to leave the
devastated planet without Janeway and Paris, since they have died
in the planet's past. Nevertheless, the timeline is changed and
the explosion is avoided this time, and this is a clear
contradiction to the above predestined sequence of events.
Anyway, a new timeline emerges in which Voyager encounters an
intact planet, and no one remembers the fatal original timeline.Classification: broken predestined timeline ("causality loop")

VOY: Eye of the Needle The wormhole in this episode leads to the Alpha
Quadrant, and it is found that it also leads back to the year
2351. The Romulan captain is advised to keep his encounter with
Voyager secret until the ship actually disappears, although he
proposed to warn Starfleet. Captain Janeway insists on this
agreement because Voyager is important for the history of the
Delta Quadrant.

The possibility of a paradox is not mentioned in the episode. The Romulan captain probably kept his promise,
and the timeline was not changed. Unfortunately Tuvok finds out
that the man died in 2367 before he could inform the Federation
about Voyager. In the alternative timeline in the episode VOY:
"Non Sequitur" it is mentioned that there has been a
memorial service for the Voyager crew. We can suppose that also
in the original timeline after "Eye of the Needle" no one knows of the whereabouts of
Voyager until the episode "Message in a Bottle".Classification: interaction with the past, probably without
consequences

VOY: Non SequiturHarry is still in the present, but it is
obviously another reality in which he is not aboard Voyager, but
in San Francisco where he is engaged in the construction of the
Yellowstone-class runabout prototype. Tom too has remained
on Earth. Harry learns that his Voyager shuttle got into a "temporal
inversion fold in the space-time matrix", or simply a
time stream, and this accident altered history.

So Harry is not in a
parallel reality (such as Worf in TNG: "Parallels"),
but in another timeline. Harry himself was obviously protected (a
meanwhile familiar concept), and he is the only person to know
about the old timeline. In order to get back to Voyager, Harry
has to find the time stream and recreate the accident. The alien
lifeform (Cosimo) tells Harry that the time stream weaves through
the galaxy, so it can be reached with a runabout from sector 001.
However, the alien can give him no guarantee of getting back, and
Harry could find himself at any time in the past or future.
Nevertheless, Harry and Tom manage to reproduce the accident,
even with a damaged runabout and without any computer data, and
Harry travels back to the exact instant when he caused the first
timeline change. Back in the original timeline, Harry is saved
from the collapsing shuttle and comes aboard Voyager, where he is
the only person to know about the intermediate timeline. A person
can hardly have more luck.Classification: alternate timeline that ceases to exist

VOY: Future's EndThe little Federation timeship Aeon under
Capt. Braxton appears from a space-time rift. Braxton pretends
that Voyager will be responsible for an explosion that destroys
all of Earth's solar system in his time, the 29th century. As a
consequence, he has no other choice than to destroy Voyager prior
to this disaster. However, Voyager fights back against the
technologically advanced yet vulnerable timeship, and both
vessels are pulled into the space-time rift. The timeship
probably came from Earth, or at least from a near space region,
since Earth itself was destroyed in this timeline. So it is no
surprise that the space-time rift leads back to Earth. The time
of arrival seems to be undefined, when the time travel is not
controlled. While the timeship crashes down on Earth in 1967,
Voyager arrives there in the year 1996. By the way, once at home,
why does Captain Janeway not take the chance and travel to the
24th century the old-fashioned way, as Kirk & crew did three
times?

In the year 1996, Braxton is nothing but a
freaky old man. Anyway, he outlines the sequence of events: "A
- There is an explosion in the 29th century. Debris from Voyager
is found. I go back to the 24th century to stop you. B - Voyager
prevents me from destroying you, destabilizing my equipment and
throwing me back to the 20th century. C - Someone from the 20th
century steals my timeship and launches it. It goes back to the
future, but makes a critical mistake that launches a temporal
explosion...and we jump back to A." In other words,
Braxton explains a causality loop in a predestined timeline.

The Voyager crew learns that Henry
Starling, a former hippie who was camping near the crash site in
1967 seized Braxton's timeship and used the technology to initiate the
microelectronic revolution. It is questionable if contemporary
technology can be derived from very advanced components. There
must have been a detailed instruction aboard how to produce
"antique" microchips that fit into history. In this
respect, Starling had only a slight advantage over his
competitors. Moreover, it would probably not help him to go to
the 29th century to get more technology he cannot use directly.
So why does he take the risk anyway, even after he has been told
that it might lead to a disaster?

It is worth mentioning
that in the real world the company Intel was founded at about the
same time (1969) and started the microelectronic revolution with
the introduction of the first integrated memories and the first
microprocessor. In the Star Trek universe Chronowerx (note the allusion to the origin of Starling's technology and the 29th
century comm badge logo) took Intel's and other companies'
places. Janeway notes that the microelectronic revolution at the
end of the 20th century should not have taken place. She
obviously read about this era in a history book or PADD, and now
she gets to know that it all happened because of a time travel.
This also points to a predestined timeline.

The destruction of the timeship with
Starling aboard should have lead to a paradox, since this
definitely breaks the predestined timeline. Nevertheless, a final
timeline emerges in which the future is changed, but not the
past, as if there were no causality. This solution is not logical
and therefore not satisfying. Moreover, a browser called "Browser
Hound" by the company Chronowerx shows up in VOY: "11:59",
although the impression is created that Starling's rise to an industry tycoon
will not happen in the final timeline. Also, it is mentioned in VOY:
"Relativity" that Braxton (or one version of him) actually spent all
the time in the 20th century, as if the timeline had not been repaired.Classification: multiple time travels, incorporating broken predestined
timeline ("causality loop"), outcome uncertain

VOY: Before and AfterThe oddity about the repeated time travels
in this episode is that Kes travels back into her own (and
younger) body each time, so it is not a solely physical, but also
a biological problem. Any attempt to explain this phenomenon is
very hard, since it is not just a matter transfer, but Kes'
consciousness is transferred from one time to another. This
raises the question what a consciousness really is and how it can
be removed or replaced. Moreover, what happens to the
consciousness of the younger Kes who is replaced by the older one
each time? Picard has similar experiences in TNG:
"Tapestry" and TNG: "All Good Things", but
his time travels are arranged by Q, and it is not clear whether
they are completely real.

Kes starts traveling back in time when the
EMH puts her into the biotemporal chamber at the end of her life
at the age of 9. In connection with the chroniton contamination,
from which she suffers since the Krenim attack a few years ago,
this treatment is the cause for her time leaps. Kes' actions in
the present appear to have no effect on the respective future.
Otherwise the Doctor, who knows about the time leaps, and also Kes
herself could simply avoid the biotemporal treatment in the
future and therefore cause a paradox. Yet, it is not clear what
will happen in Kes' future after she has traveled back and if she
will have a future at all. Each time Kes arrives at an earlier
time and tells what she is going through, the Doctor attempts to
stabilize Kes' condition and keep her in the respective present.
The question arises if this is really necessary and if it makes
sense at all. After all, there was another Kes in the respective
present before the Kes from the future took her place. Maybe
there is a risk that as soon as the future Kes is further in the
past, Kes will disappear in the present and future. In this case
Kes would finally cease to exist as a living being once she
reaches an instant before her procreation. This possibility is
briefly hinted at in the episode.

The Doctor's repeated attempts to stabilize
Kes finally succeed in the "present", i.e. at the time
between the previous and the following episode. Nevertheless, Kes
is being shown traveling back even to an instant prior to her
birth, while she is simultaneously in sickbay. This could be the
decisive hint what happens when Kes has gone for another time
leap. Her body in sickbay might remain unconscious without a
chance that consciousness is ever regained, since it is on a time
travel. Furthermore, it has to be mentioned that it is the Kes
from the future who remains in the present. Due to the strange
cerebral decay, which is being reversed while she travels back in
time, she only remembers part of her future, and it is
questionable if she remembers many things of the present and
past. Anyway, she is not the same person that she was earlier at
this age. However, this seems to be no problem in the following
episodes.

Side note It is noticeable that Kes suddenly has long
hair in the present. This is definitely not attributed to her
time travels, since not her body but her consciousness is
traveling.

At the end of the episode, Kes tells about
the (possible) future, and Tuvok is obviously interested in
getting to know more about the Krenim. Nevertheless, at the very
time of the first Krenim attack in VOY: "Year of Hell", all of Kes' knowledge of the future is gone. Neither
Tuvok nor anyone else remembers what Kes told about the Krenim
and their chroniton torpedoes, and of course there is no defense
against them. This could be regarded as another inconsistency,
unless it is taken into account that in "Before and
After" Kes travels back from a future that ceases to exist
at latest when she leaves the ship in VOY: "The Gift".
In other words, all events that have been shown in "Before
and After" actually never took place or will never take
place in the new timeline, when Kes is not aboard Voyager. The
question remains how Voyager could make it through Borg territory
in the original timeline without Kes leaving the ship and pushing
it 10,000 light years towards the Federation territory. Vice versa, in the
old timeline Seven of Nine is not there to help the crew in
several critical situations. Notwithstanding these significant
differences, in both timelines Voyager encounters the Krenim at
about the same time.Classification: "biological" time travel

VOY: Year of Hell"Year of Hell" does not
exactly feature time travels, but "temporal
incursions". Although the principle of temporal incursion is
not sufficiently explained in the episode, the impact is
discussed or becomes evident several times. The Krenim scientist
Annorax designed the incursion device with its temporal core and
the weapon ship on which it is installed in order to turn it
against the enemies of his people. Annorax' first
incursion made the Krenim powerful again. Fate turned against him
when he unintentionally eradicated his family with the second
incursion, and this makes him a tragical character rather than
just a villain ("You're a long way from home, and in a
manner of speaking so am I").

The temporal incursion weapon is focused on
a target object, which is then removed from our space-time. Not
only will the respective object disappear in the present, but
also in the past and future. In other words, the target has never
existed in what we regard as our history. The question where the
target object exists after the incursion, if not in our
space-time, is not answered, however, this is of minor importance
for the further discussion of the episode. How can the effect of
temporal incursion be accomplished? The first possibility is to
trace back the object's history and continuously or frequently
remove it from space-time, which corresponds with Annorax'
statement: "I can control the destiny of a single
molecule or an entire civilization". Still, the
probability to get the right trace in a time many millennia ago,
let alone back at the instant of the Big Bang, is virtually zero.
After all, this method justifies the extremely complex
calculations that are necessary for an incursion. The second
method implies a kind of "anti-time" reaction similar
to the one featured in TNG: "All Good Things". Once
applied to the object in the present, the incursion wave travels
back to the past and continuously erases the object. In this case
the calculations are necessary to simulate the effect and not to
control the weapon itself. However, their complexity is probably
the same.

Eradication of the target itself is the
primary effect of temporal incursion. Apart from this, the
disappearance of the respective object will entail more or less
severe consequences, which can be regarded as secondary effects.
For instance, the comet Chakotay proposes to erase in order to
alter Voyager's course in the past carried organic molecules that
allowed the formation of life on a planet. The inhabitants of the
planet finally colonized many sectors of space. Erasing the comet
would cause 8000 civilizations within 50 light years to disappear. This is
where temporal incursion is equivalent to time travel, and where
paradoxes may occur. In other words, temporal incursion is
similar to traveling back to ancient times, removing an
object and taking it along to the future, with all potential
consequences. Taking into account all possible secondary effects,
Annorax calculates a "focal point" each time at which
the weapon is directed. In this way it is not necessary to
destroy a whole planet, but only some decisive man-made objects
in order to eradicate the whole civilization on the respective
planet and leave nature intact. This is shown in several VFX
sequences, and it is noticeable that primary and secondary
effects cannot be distinguished, since they become evident
simultaneously. It remains Annorax' secret how he gathers all the
necessary information from the past. The data volume must be
incredibly high.

The sequence of events is probably the most
complicated ever shown in Star Trek. The following table provides
a survey of the temporal incursions that have been shown or
mentioned in "Year of Hell":

Time

Incursion #

Goal

Target

Effect

Some
200 years ago

Original timeline

-

-

The
Krenim wage war against several enemies. Annorax builds
his weapon ship to eradicate the enemies and make the
Krenim powerful again.

Some
200 years ago

1

Restoration
of Krenim Imperium

Rilnar
Homeworld

The
Rilnar, enemies of the Krenim Imperium, are erased, and
the Krenim become much more powerful. However, an
antibody that the Rilnar have introduced disappears as
well, and 15 million people die of a disease for which
there is no cure in this timeline.

Some
200 years ago

2

Unknown

The
primary effect of this incursion is unknown, anyway, the
remote outpost on Kyana Prime is erased as well together
with Annorax' family.

During
the last 200 years

3..x-1

Restoration
of Kyana Prime Colony

Numerous

The
Krenim Imperium is never completely restored, neither is
Kyana Prime.

Day 1

x

Zahl
outpost

A Zahl
outpost is erased, which has minor bearing on the
timeline, and the Krenim territory remains small. Voyager
encounters a harmless Krenim patrol vessel.

Day 4

x+1

Zahl homeworld

The
Zahl Homeworld is erased, which leads to a 98%
restoration of the Krenim Imperium (849 worlds, 5000
parsecs in diameter), but Kyana Prime is not re-established. Voyager is now under attack by a powerful
Krenim warship. No one aboard notices the timeline
change.

Day 65

x+2

Garenor homeworld

The
Garenor Homeworld is erased, but Voyager's temporal
shields interfere with the temporal shockwave such that
the Krenim Imperium is reduced to a few planets. This
time the Voyager crew is aware of the timeline change.

Day 70

None

Eradication
of Voyager

USS
Voyager

Annorax
attacks Voyager with his weapon, since the eradication of
the Federation ship would probably lead to the desired
effect of incursion #x+2. However, Voyager's temporal
shields hold.

Day 207

x+3

Restoration
of Kyana Prime Colony

Ram
Izad homeworld

The Ram
Izad civilization is erased, which entails a 52%
restoration of the Krenim Imperium.

Day 257

x+4

Eradication
of the attacking fleet

Two
Nihydron vessels

The
incursion beam penetrates the temporal shields, and the
vessels are eradicated.

Day 257

x+5

Restoration
of original timeline (Janeway)

Janeway
rams Annorax' ship

A
temporal incursion within the weapon ship occurs, so the
ship erases itself. Since the ship has never existed,
history is reset to a state that was prior to the first
incursion. Nevertheless, this timeline is different from
the original one.

A temporal shielding serves to protect
Annorax, his crew and ship from the impact of temporal incursion
and to avoid paradoxes. This is necessary, since any incursion
Annorax carries out in order to restore the Krenim Imperium will
almost certainly lead to a situation in which the incursion ship
is not needed and will never be built. Second, even if the
existence of his ship itself is not impaired by the incursion,
Annorax would not be able to "enjoy" the effect he has
achieved, if he is affected himself by the timeline change and
does not notice it. The shielding implies that his ship is out of
our space-time. Nevertheless it is visible. Maybe its
principle is similar to the chroniton particles that protect the
Defiant in DS9: "Past Tense". The question arises
whether the shielding is necessary only during the incursion or
all the time. In the latter case Annorax and his crew would have
to stay aboard for all future in order not to be affected by the
timeline change, which would not be very pleasant for them. When
the fleet attacks the weapon ship on day 257, first officer
Obrist turns the temporal core offline which causes the temporal
shielding to fail. Annorax notices that the ship "is
phasing back into normal space-time", which indicates
that this is a continuous process, but it does not become clear
in which way the crew is affected by this process. If the
shielding is necessary all the time in order to preserve the old
timeline within the ship, it is self-evident that the lock of
hair of Annorax' wife disappears, since she has never existed in
the timeline outside the ship. In this case, however, Annorax,
his crew and ship who do not belong to the external timeline as
well should have vanished at the same time. Still, the ship
eventually disappears as late as it is erased through
self-incursion after Voyager has rammed it. While the nature of
the weapon ship's shielding is not clear, Voyager's temporal
shielding can obviously be turned off without the crew and
computer forgetting the old timeline.

It is stated that Annorax and his crew have been spending some 200 years aboard their ship. He also claims: "As
long as we are on this vessel, protected from space-time, we have
all eternity to accomplish our mission." Nevertheless,
irrespective of temporal shielding and other effects, if the crew
have experienced and measured 200 years, they must also have aged
accordingly, unless the shielding implies unknown biological
effects that prolong life. The only explanation for this
phenomenon is that the Krenim are a very long-lived species.

The temporal incursion propagates in the form
of a temporal shockwave that implies a discontinuity of
timelines. The new timeline applies to the region the shockwave
has already passed, while the old one is still existent in the
region in front of the wave. The shockwave is obviously a
subspace phenomenon and travels at warp speed, since it would
otherwise take many years before the effect becomes evident in a
distant region of space e.g. when the Garenor Homeworld is
erased, 20 light years away from Voyager. However, each time the weapon is
applied to a target, as shown in the nice VFX scenes, the wave
propagates at a speed that can easily be perceived with the eyes.
The effect is obviously shown in slow motion to emphasize it.

The undetonated chroniton torpedo is
located in the Jefferies tube on deck 11, section 2 in
"Before and After" as well as in "Year of Hell", and is examined by Kes and by Seven of Nine,
respectively. This is a very improbable coincidence, taking into
account that the timeline was significantly changed when Kes left
the ship and Seven came aboard. Moreover, in "Before and
After" Captain Janeway and B'Elanna die in the first Krenim
attack, whereas in "Year of Hell" only "Ensign
Insignificant" is killed. The fact that the chroniton
torpedo has the same temporal variance of 1.47 microseconds each
time is not necessarily a coincidence, since this might apply to
all torpedoes.

On day 1, Voyager encounters a Krenim
patrol ship or warship three times in three different timelines.
The Krenim commander is the same person each time, which is not a
sign of consistency but highly improbable. At least, in the final
timeline, the encounter takes place before the astrometric lab is
presented, whereas it has been afterwards in the first two
versions.

The scene in which Voyager rams the weapon
ship is connected with a number of problems. First, Janeway must
be very desperate to hope that destroying the weapon ship will
lead to a self-incursion, yet she seems to be sure about it ("Time's
up."). She should have taken into account that even if
Annorax' ship survived the probable explosion of Voyager's warp
core, the temporal core would be too heavily damaged. Second, the
temporal core is not working any more at this time, since Obrist
took it offline, nevertheless it causes the self-incursion.
Third, if a temporal incursion within the ship erases the ship
together with Annorax and his crew, they will not exist any more
in the new timeline, since this is what happened to all objects
that have been eradicated before. However, at least Annorax does
exist in the final timeline, and this fact leads to a paradox. If
the original timeline prior to the first incursion is restored,
Annorax will certainly build his ship again and all history will
repeat, leading to a causality loop. In this case Voyager could
not escape as well and would be destroyed each time ramming
Annorax' ship. Nevertheless, the timeline shown at the end of the
second part is definitely different from the one in which Voyager
and Annorax destroy each other, since the first encounter with
the Krenim patrol ship is prior to the demonstration of the
astrometric lab this time. It is still possible that Annorax
carries out temporal incursions in this timeline as well, and
might affect Voyager. It becomes evident as late as in the following
episode that the "Year of Hell" does not occur all over again.

In this context the final scene of
"Year of Hell" is the most ingenious ever seen in
Star Trek. Not only does the scene show Annorax together with his
beloved wife, whom he tried to get back for 200 years and
actually got back when he was defeated. The scene also leaves
multiple possibilities of interpretation what is actually
happening. The scene could show Annorax making his first
calculations some 200 years ago, which could be a sign that he is
about to build the incursion weapon and history will repeat. Or the fact that he drops the PADD with "a few more
calculations" in order to care about his wife could be
a sign that he is more sensible this time. Or the scene could
take place in "our" present, i.e. at about the time
when Voyager passes Krenim space. In this case it is obvious that
history was altered and Annorax had a lucky life together with
his family. Still, his PADD indicates that he might build his
ship, fortunately too late to affect Voyager.Classification: multiple past incursions to change history, without physical
time travel, corrected

VOY: Timeless The attempt to get Voyager home using the newly
installed quantum slipstream drive turns into a disaster. The
ship drops out of slipstream, runs out of control and crashes
onto an ice planet. The crew is killed, except for Harry and
Chakotay aboard the Delta Flyer who remain in slipstream and
finally reach Earth. Fifteen years later, the two officers try to alter the past. They steal the Delta Flyer and a Borg temporal
transmitter to send a message to Seven of Nine in the past,
consisting of new course correction data to keep the ship in the
slipstream. The attempt, however, fails and the ship is
nevertheless destroyed. Time is pressing, since the Delta Flyer is
pursued by the USS Challenger commanded by Capt. Geordi La Forge, who has been ordered to prevent the violation of the
Temporal Prime Directive under all circumstances. Without the knowledge how
to maintain a stable slipstream flight, Harry decides to send new
data back to the past to collapse the slipstream, in order to save
the crew's lives at least. This time he succeeds. Seven receives
the message, the slipstream is shut down and the ship is safe in
the past.

The Delta Flyer explodes due to a warp core
breach just after the message to the past has been sent,
indicating that the respective timeline continues for at least a
few seconds. This timeline, however, is supposed to disappear
immediately, as soon as the past is changed, unless the
transmission to the past is connected with a delay. It is obvious
that there should be at least a delay due to the spatial
distance, even if Borg subspace devices are employed.
"Timeless" features the usual grandfather paradox, where the past is
changed from a future that will eventually cease to
exist. When Harry asks her to explain this paradox at the end of the
episode, Janeway responds "Don't even try". I am not
sure if this is a sign of wisdom or of ignorance. Anyway, it is a
good suggestion in this case.Classification: past incursion to change history, without physical time
travel, successful

VOY: Gravity One of Voyager's shuttles gets sucked into a
gravity well and crashes on a desert planet. Tuvok and Paris are
trapped on the planet for months while only a few hours elapse on
Voyager. The problem is that, according to general relativity,
time in a high gravity region should elapse slower and not faster
than outside. On the other hand, the planet's gravity is
obviously in the normal range, which points to something different
than a relativistic effect. In other words, there must be a
region of normal gravity embedded in the high gravity region.
Therefore it should be rather one of the strange Trek phenomena
made responsible for both the gravity and the dilation effects.Classification: different time levels

VOY: Relativity Calling this episode "complicated" would
be a mild understatement. It's hard to analyze a time travel
episode that consists of intricate paradoxes, but I will
nevertheless try it.

1. "Relativity" begins at Utopia Planitia
when Voyager is just being prepared for the first mission in
2371. Seven of Nine, disguised as a Starfleet ensign without Borg
implants, is supposed to detect the temporal disruptor that will
destroy the ship about four years later. She has been hired by
Capt. Braxton from the 29th century, who wants to examine the
accident. Although it was not explicitly stated, I think his
motivation is not to rescue the ship in the first place, but the
temporal device comes from his time and would be a violation of
the Temporal Prime Directive that has to be prevented.

Seven creates the first potential paradox
when she meets Captain Janeway and Joe Carey. What might happen
if they recognized her when she comes aboard in
"Scorpion" and her human physiology is restored in
"The Gift"? Their actions in the future might be
considerably different, and Braxton's crew might not be able to
beam out Seven in the first place in 2375. It is not a
predestination paradox, since Janeway definitely doesn't know
Seven in "The Gift", so the future is actually in
danger.

Seven is obviously able to see the temporal
device, which is not only out of phase but not even in place yet
as of 2371. I wonder how she can see into the future which has
never been mentioned so far. Anyway, this scene is a clear
mistake, since she can't perceive the device during the Kazon
attack (see act 2) in 2372.

When Seven returns to the 29th century, she
dies on the temporal transporter platform. Too bad. However,
Braxton, has a simple solution just to retrieve Seven once again.
His assistant says they have already used her before, and that a
forth jump would cause "neural damage, even temporal
psychosis". The accumulative damage is obviously a trick
to increase the thrill of time travel, however, it makes no
sense. Every time Seven is going to be drafted again, it has to
happen a bit earlier, and the "fresh" Seven wouldn't
have been damaged before. They would only need to take care that
the same copy of Seven is not transported too often.

2. This act begins in the present, i.e., the time
prior to the explosion of the ship in 2375. There are a few
"minor" effects, for instance the ping-pong ball that
stands still. There are supposed to be some paradoxes too, the
most obvious being the Doctor's premature arrival in the mess
hall, before Neelix actually calls him. The paradox is that after
the Doctor has already arrived there is no need to call him in
the first place. BTW, why didn't the Doctor try to call himself,
just for fun? :-)

Back in the Jefferies tube once again (or
the first time from her point of view), Seven can see the device,
which is out of phase but actually there. Just before the ship
explodes, two crewmen of the Relativity appear and transport her
to the future. I wonder what Braxton meant by "retrieve
Seven of Nine a microsecond before the explosion". The
two men can hardly have such a precise timing. Moreover, I wonder
how they got hold of Seven the first time. Shouldn't there be two
other men also waiting for her? What about this paradox: By
getting her a second time, wouldn't they prevent the first time
from happening?

Anyway, Seven is now being prepared for her
next mission. She learns that she has done this already twice
before. So there was a mission 1 we haven't seen and the
aforementioned fatal mission 2. Obviously the forth time that becomes dangerous is supposed to refer to the complete mission,
which consists of up to four transports altogether (2375 to 29th
century, 29th century to destination and back, 29th century to
"re-integration" - unless she is dead by then).

There is a mistake from the part of Seven
of Nine when she is supposed to give an example of the Pogo
paradox aka predestination paradox, "a causality loop in
which interference to prevent an event actually triggers the same
event". She refers to the events of "First Contact". However, there was no predestination involved, since Earth was
definitely assimilated when the Borg had vanished to the past,
which would not have been the case if their failure had been
predestined. If there was a causality loop, it could have been as
well that the Enterprise tried to prevent assimilation of Earth,
but unintentionally helped the Borg doing so. ;-)

This time Seven is transported to the year
2372, or to be very precise, stardate 49123.4621. This
corresponds to the early second season, prior to
"Maneuvers". As already mentioned, she can't detect the
device now, which is no surprise, since it's not yet there.
Therefore it becomes a mystery why she could see it at Utopia
Planitia. When Janeway and Tuvok contain her inside the
forcefield, it's the usual "I'm from your future" game
and if the encounter at Utopia Planitia wasn't already a paradox,
this is definitely one, and Braxton is not very happy about it.

The story becomes really weird when the
second Braxton appears. This Braxton is supposed to be older than
the one on the Relativity, so the latter can't know about him. So
far, so good. Yet, old Braxton claims he has actually experienced
the 30 years on 20th century Earth, as it was shown in
"Future's End". This statement left me baffled. Didn't
Braxton show up at the end of the episode and he was all right?
Agreed, this was obviously a younger version who might *not yet*
have experienced this timeline. Yet, the impression was created
that the complete sequence of events, including the encounter
with Voyager, Braxton's crash on Earth, Starling's flight to the
29th century and the disaster in the solar system, were
extinguished at the very moment when Voyager destroyed Starling's
stolen timeship. If this was not sufficient, the young Braxton that was obviously able to scan time should have found a means to
prevent his unintentional stay in the 20th century from
happening. Even if the timeline of 20th century Earth wasn't
changed, was the old Braxton rescued from this time by his
colleagues? This is actually the only reasonable explanation, I
only wonder why they needed 30 years. This could be the case if
there was already a Braxton in the 29th century, and the one in
the 20th century was just forgotten - how thoughtless. After his
return the two were probably re-integrated, and the memory of the
20th century eventually prevailed. On the other hand, there
should be two versions of the 29th century: one in which Voyager
was destroyed and Braxton is more or less successful in his job
(as shown on the Relativity) and one in which a (future) Braxton
sees a need to destroy the ship which has not happened until
then. Now it's really getting too complicated: another paradox
within the paradox. In my diagram the "Mad Braxton"
timeline and the main timeline should be tied together in some
way, but I didn't know a solution, so I kept them separate.

3. Seven is transported again, and it's allegedly her fourth time, just when it's supposed to become dangerous. As
already mentioned above, I can't reproduce the strange
mathematics of accumulative damage through time travels, so I
won't comment on it. Anyway, Seven is now running through the
corridors of Voyager at Utopia Planitia and shooting at Braxton,
and is causing a hell of a paradox, but without obvious
consequences.

4. It's now the fifth transport, if we still believe
it. In 2375 Seven meets Seven and a couple of other crew members
enjoying a table tennis match, just a second before the set point
with Paris' inimitable "still ball" trick. Braxton is
arrested, the case can be closed. Really?

5. It is now up to Janeway to clean up the timeline
and prevent everything from happening in the first place (maybe
she should go back to the Big Bang, then ;-)). Anyway, she has to
stop Braxton once again, before he can install the bomb on
Voyager, and I have another problem. This would be the ultimate
paradox, unless the timeship is shielded against changes in the
timeline, and even this would not sufficiently solve the problem.

Anyway, we get to know that different individuals who were separated by the creation of different timelines
can be re-integrated. This is a rather elegant solution to the
problem what to do with persons from extinct timelines. And it is somewhat
similar to what was done with Capt. Christopher in TOS:
"Tomorrow is Yesterday".

Not a track plan, but a summary of time travels in
"Relativity"

The diagram shows the sequence of events in
"Relativity". Every time travel is supposed to create
another at least slightly different timeline. The diagram shows
only the three main timelines. If it were more detailed, it would
not only be unreadable, but would also reveal that persons would
frequently travel to timelines that don't exist anymore, in other
words, the paradoxes would show up in the form of countless
question marks.Classification: multiple past incursions to change history, corrected,
involving "temporal
re-integration"

VOY: Blink of an Eye This adorable episode shows how a planet on which time passes in
a blink of an eye interacts with the rest of the universe, and with Voyager in
particular. So it's not really a time travel, but something closely related.
Essentially, the problems are the same as in TOS:
"Wink of an Eye" and TNG:
"Timescape", considering frequency shifts that occur with every
transition from one timeframe to another. Some problems of this specific episode
were unavoidable to build the plot, but some others were simply careless.

First of all, a planet spinning at 58 revolutions per
minute is not likely to maintain its cohesion for long - unless gravity is
immensely high which would forbid any life on the planet or unless there is an
effect involved that needs some technobabble to be explained. The latter seems
to be the case here, and the tachyon core of the planet might be responsible for
its strange behavior as well as for the fact that Voyager is stuck in its orbit.
This leads to the next question: Did Voyager cause the temporal differential or
was the planet always so "fast" compared to the rest of the universe?
The statement saying that the tachyon core has created the differential is not
definite. If the planet had always been out of time, this would explain why it
is revolving so fast as seen from a distance. Yet, it would be an exceedingly
unlikely
coincidence that Voyager arrives the very week when the civilization is
developing both iron processing and warp drive. If Voyager caused the
differential by becoming the third pole, the planet would return to the normal
timeframe as soon as the ship left. This, however, does not seem to be
the case at the end of the episode when the astronaut Gotana-Retz says: "I'm afraid it'll be a while before my people actually join the rest of the
galaxy." What would still hinder them, considering they now have all the
required technology?

A related question is how there can be day and night and
even seasons on the planet. If the central star is similar to our sun and the
planet's orbit is similar to Earth's, one round would take several centuries. If
life on the planet has always been accelerated, this means that some other
effect than a tilted ecliptic must be responsible for the seasons. If Voyager
had caused the time dilation, most life on the planet would have probably
perished after a while. The arguments concerning day and night are similar. The
planet spins at 58 rounds per minute which would allow a reasonable
day-and-night period only if time itself were equally accelerated. The rotation
rate of the planet perfectly complies with one of the contradictory figures
given for the time differential (see table below). This can't be a coincidence.
If Voyager were responsible, then life with days that last only a second would
have been very strange before Voyager's arrival. So it is almost safe to say
that the planet was always that fast. It's hard to explain physically, but
logically it's necessary.

Like in the above TOS and TNG episodes, the frequency
shift inconsistencies are obvious. The blue shift of radiation and radio
messages from the planet is more or less consistent, neglecting some
quantitative errors. Vice versa, Voyager would not be visible, but would appear
extremely red-shifted on the planet. If at all, the people down there could make
up merely a weak heat radiation source. The only way that Voyager's visibility
could be explained would be that some ultra-high frequency radiation from
Voyager's shields is converted to visible light. The problems concerning life on
the planet become worse when we take into account that the radiation emissions from
their central star are red-shifted too. If the star is similar to our sun, only
a weak heat radiation would arrive on the planet, hardly enough to maintain
life, let alone provide daylight. The only explanation is that the star is
emitting very large amounts of x-rays which appear like a normal solar spectrum
on the planet. Even if we can explain this, there is no excuse that the two
astronauts can see anything aboard Voyager and even feel that B'Elanna's hand is
warm (which should have a temperature slightly above 0K in their timeframe). It
was a bad idea anyway to let the two astronauts remain in their timeframe for a
few minutes after they have entered Voyager, for which there seems to be no
reason. We could make up a theory that the masses of their ship and their bodies
have "dragged" some of their space with them (which might also explain
that they are able to break through Voyager's shields), but this neither complies
with real physics nor with Trek science as shown so far. In addition, the
capsule did lose contact with their control center already while approaching
Voyager, insinuating that they were already slowed down at that time. The
dizziness or even trauma when entering another timeframe, on the other hand, is
consistent with the two other Trek episodes that feature different time levels.

Many figures concerning the time
dilation are stated, and there are a few annoying calculation errors. I'm
considering to create a little pocket calculator tutorial for the responsible
authors, especially conversion from decimal to hours, minutes and seconds. This
is a short summary of the figures:

Statement

Ratio
(planet time / Voyager time)

Planet
rotates at "approximately 58 revolutions per minute". (Tuvok)

83,520

"For each second that passes on Voyager, nearly a day goes by on the planet."
(Seven)

86,400

"When it reached our time frame the frequency would be
thousands of times higher than normal." (Chakotay)

>
1,000

Time
passed on the planet from receiving the message to the senior staff
meeting: "nearly a century by now." This would mean it took a full
ten hours to call for the meeting.

-

"I'm keeping you down there for three seconds, Doctor. That will be almost two days in their time frame."
(Janeway)

<
57,600

The
Doctor remained on the planets probably for several minutes, which was over three years to him. This is consistent if it was about 18 minutes,
but it seemed less.

-

"The sensors detected an early
test." Four seconds period. "Another test - six weeks later."
(Seven)

907,200

In addition, why doesn't Gotana-Retz return
sooner to the planet? One hour would equal about one decade. He might have the
chance to see his friends and relatives again, but spends a lot of time talking
to Janeway, until he is finally "allowed" to leave because the ship is
in danger. Finally, at the end of the episode we see an old man watch how a star
disappears from the sky. I am pretty sure this is Gotana-Retz, but how is this
possible, considering that Voyager should already be gone for many planet years?
Well, he may have returned, and while Voyager was still undergoing repairs for
one hour, as mentioned in the episode, he may have aged accordingly on the
planet.Classification: different time levels

VOY: Fury The grandfather paradox in this episode is quite obvious: Old Kes
goes back to the past to betray her old crew to the Vidiians, and she is killed
there. Janeway, Tuvok and, last but not least, young Kes herself keep the
knowledge of this incident. When old Kes is about to travel back again, Janeway
can convince her to stay in the present. I think the logical problem is not that
much the paradox itself, as we have encountered countless times before, but
the fact that Kes's time travel and the Vidiian attack have no effect t all on
the present, and most notably Kes doesn't learn anything from it. As if nothing
had happened, she evolves to the very same bad old Kes
for a second time, who, at the very same time
(just after Janeway has replicated Tuvok's birthday cake) pursues the very same
revenge plan. This can't be simply explained by something that wiped out her
memory, since even then she would have behaved differently. Moreover, when she
was talking to Janeway at the end of the episode, it was obvious she did remember
everything indeed.Classification: past incursion to change history, corrected

VOY: Shattered So we have a ship that is split into 37 (not 47 ;-)) sections, and
each of them is in another time. At first it is only Chakotay, who is able to
cross the barriers between the frames. So far, so good. The key question is if
the ship as a whole is intact or if there are only certain sections existent in
certain times. In the first case, if the ship is intact at every time and in
every place, it would be only Chakotay's special chroniton inoculation that
makes him cross the barriers that, for some reason, can be found in certain
locations on the ship. This would be a bit like in DS9:
"Visionary" where there was something special about O'Brien, and
some other effect (from the cloaked Romulan ship) caused him to jump ahead in
time, and also TNG: "Parallels" where
Worf entered different quantum universes, triggered by Geordi's VISOR. We
could explain the whole mess in that Chakotay is just running through time, and
it is actually him who is screwing up everything in the first place. This is regrettably
(with regard to logic) not the case, as is pointed out in the
episode several times, so we have to go with the very implausible alternative.

According to what is stated in the episode
itself, the ship is split into different time frames, and in each time frame
only a fraction of it exists. This is evidenced by Seska who states that they
are not able to leave engineering. Another hint is that Seven can't be found in
Naomi's and Icheb's future time frame, and she is supposed to be in another one.
Actually, every person can be found uniquely in one time frame, but this is
still another problem to be discussed. Another reason why the ships in the
single frames are not intact, even before Chakotay's interference, is that
Janeway tells Chakotay of malfunctions before Voyager is entering the Badlands
that didn't occur in "Caretaker", so history was already changed.
Finally, everyone, even Seska, sees the need to fix the whole mess, so in every
time frame it has been noticed there is something wrong with the ship.

This is where the logical problems really
start. It is quite obvious that a ship of which only a part exists in each time
should have malfunctions - this term being a mild understatement, for most of the
ship in most times should be without power and maybe without life support.
Nothing physical can cross the barrier, be it a person or a communicator signal,
so why is the ship in almost perfect shape in every time frame? And while
everyone is talking about what is going on inside the ship, what is happening
outside? Is the whole ship with its different time frames in one place and time
in the universe, preferably at its last position prior to being hit by the
anomaly? What has happened to the ship at Seska's time, for instance in this
case, if part of it is not there any more? It seems much more likely that each
section in its respective time and place and, the other way round, the other
Kazon can't get into engineering just like Seska can't leave it.

The next problem is that Chakotay is able to
leave engineering, and when he does, Seska and the Kazon can't see him any
longer, but he can still see them. We know that there is something special about
Chakotay, and when he can cross the barrier, it is somewhat plausible that he
can look through it too. The actual problem is that Seska (or the camera showing
the scene from Seska's view) can see anything of the upper level of engineering.
What she sees can't be in Chakotay's time frame because why should she be able
to perceive the environment, but not him, so it must be Seska's own time frame.
But isn't it that she is confined to a certain area? The same applies to the
officer who was with Chakotay and Janeway, and who can see the rest of the
corridor in which the two have just vanished. The only explanation left is that
somehow the time frames have no sharp edges, but they overlap a few meters.
Also, just before Chakotay leaves engineering for the first time, a Kazon gun is
thrown through the barrier. So other people or objects are able to cross it too,
or is it only because Chakotay touched the gun? On the other hand, his medikit
doesn't go with him when he first crosses a barrier. In addition, Janeway says
that her helmsman (Lt. Stadi) "disappeared when she tried to walk down that corridor."
Where is she, still in the same time frame, and just no one bothered to search
for her, or in another time frame just like Chakotay? If the latter applies, why
isn't every person able to cross the barrier (which would have caused *a lot*
more confusion). The "Macrocosm" virus that pursues Chakotay and
Janeway in the corridor obviously doesn't make it into their new time frame, so
when they see it run into the barrier, it may actually bounce off and we only
don't get to see how it goes back - or does it disappear, like Stadi, to some
unknown third place?

The final problem, as already mentioned, is why each person only
exists in exactly one certain time frame:

Just
before entering the Badlands in "Caretaker" - bridge - Janeway,
Harry

Just
after the events in "Caretaker" - transporter room - B'Elanna

During
"Basics" - engineering - Seska

Early
3rd season - sickbay - Doctor

During
"Macrocosm" - corridor - no one special

During
"Scorpion" - cargo bay 2 - Seven

Mid 4th
season, possibly during "Waking Moments" - corridor - no one special

In the
present - mess hall - Tom, Tuvok, Neelix

17
years into the future - astrometrics - Naomi, Icheb

Agreed, this is somewhat plausible if only part of
the ship exists in each time frame. If Voyager were intact at every time,
Chakotay could meet any of the 150 crew members at any time, including himself.
But if the ship is really split, why is it that coincidentally each person (at
least each of the main characters) is in exactly one place and time frame? Harry
and Janeway are on the bridge when the ship runs into the anomaly and they are
again on the bridge in the time just before entering the Badlands, but all other
crew members find themselves in a different place than before. So we may assume that
when the anomaly strikes Voyager, it creates time frames at random, and
therefore creates situations at random where any person can be in a timeframe or
not. Following a simple probability assessment, we will likely find quite a few
different people on the bridge (to whatever time frame it may be transferred),
including Janeway, Harry, Tuvok, Chakotay and Tom. We may find another Janeway
in her quarters, perhaps another Tom in the holodeck (why is it that the program
was running alone?), and so on. On he other hand, the division of sections and
time frames may be such that certain persons don't exist at all. If many of the
time frames are before Seven came to Voyager, and accidentally there is no time
and location (note the logical AND between them) with Seven in it in the rest of
the ship she may not exist at all. And why is it that there is a time frame
containing Seska and the Kazons, but none with Kes, who spent a lot more time on
the ship? Classification: multiple time frames, corrected

VOY: Endgame The problem is the good old grandfather paradox, much like already
in "Timeless". The only difference is that this time there is a
physical time travel when Admiral Janeway comes from the future to change her
past. She is successful and, besides taking Voyager home, the Borg suffer a
disastrous defeat and the Federation now has knowledge of technology that
shouldn't exist for another 27 years. With history so drastically changed, it is
obvious that Captain Janeway wouldn't have to repeat Admiral Janeway's trip to
the past 27 years later. Nevertheless, this seems to be exactly what the Borg
Queen thinks when she strives to destroy Voyager while the ship is in the
transwarp conduit. Maybe the Queen was delirious after she had assimilated the
pathogen.Classification: past incursion to change history, successful